Defending champion Zheng Jie was a first round casualty at the ASB Classic in Auckland, losing to rising American star Jamie Hampton 7-5 6-1.
Svetlana Kuznetsova was also sent packing on the opening day, beaten in a three-set marathon by another player to watch in 2013, Kiki Bertens of Holland.
Zheng, the fourth seed, raced into an early 3-0 lead, but the young American - whose has risen from 137 to 70 in 2012 - hit back to level it up at 5-5.
She then broke the Chinese star to love and then held, sealing the set with a stinging ace.
The second set was all Hampton, her big weapon - her forehand - too much for Zheng.
Bertens, 21, is another who has shot up the rankings in the last 12 months, moving up from 184 to 63 but Kuznetsova - playing her first match since suffering a knee injury at Wimbledon - is probably her biggest scalp yet.
Bertens struggled with her service in the blustery conditions, serving 10 double faults, but she still had too much for the veteran Russian, winning 6-7 (5-7) 6-2 7-5.
American Christina McHale was the second seeded player dumped out on the opening day, the No 7 seed losing 6-4 6-1 to France's Pauline Parmentier, 6-4 6-1.